Fluid operated multi-plate friction devices generally have a disc pack consisting of one set of friction plates drivingly connected to a first member, such as a hub, and another set of friction plates alternately spaced of the first set drivingly connected to another member, such as a housing. The friction device is engaged by a fluid operated piston which causes frictional torque transmission between the members through the alternately spaced friction plates.
When the device is initially brought into engagement, a speed differential is present between the friction plate members which can result in some wear. The wear will result in increased free-running clearance in the device and therefore increased engagement time. While this slight change in engagement timing is not detrimental, it can be perceptible and requires, at least in electronic controls, that some control adjustments be made.